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It was hailed as a groundbreaking experiment to detect what happened in the first billionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang.

However, following a rash of criticism, the researchers behind the experiment hailed as a massive breakthrough have admitted they may have made a mistake.

On Thursday, the BICEP2 collaboration formally published its research in a peer reviewed journal - Physical Review Letters (PRL) - and a key researcher admitted even he has lost some confidence in the original results.

Gravitational waves from inflation generate a faint but distinctive twisting pattern in the polarisation of the cosmic microwave background, which is the afterglow of the afterglow of the Big Bang

In the paper, the US-led group stands by its work but accepts some big questions remain outstanding.

'Has my confidence gone down? Yes,' Prof Clem Pryke, from the University of Minnesota, told his audience at  a public lecture in London.

The experiment was hailed as a look at the very brief moment of time at the beginning of everything when the universe expanded very rapidly - a theory called cosmic inflation.

However, researchers now say the team did not take into account dust in the Milky Way Galaxy which may have rendered their readings useless.

Two independent analyses now suggest that those twisting patterns in the CMB polarization could just as easily be accounted for by the dust.

The team say there simply isn't enough data to rule out the dust theory.

'[Our] models are not sufficiently constrained by external public data to exclude the possibility of dust emission bright enough to explain the entire excess signal,' it writes in the PRL paper.

'Based on what we know right now… we have no evidence for or against gravitational waves,'  Uroš Seljak, an astrophysicist at the University of California, Berkeley, a co-author of one of the latest studies, told Nature News.

However, James Bock, a physicist at the California Institute of Technology in Pasadena and a co-leader of the BICEP2 experiment, said that although his group's main paper 'has been revised based on many referee comments and resubmitted' for publication, the evidence for gravitational waves 'is certainly not being retracted'.

The problems are the latest in a series of claims that the experiment was flawed.

Online rumours earlier this year also claimed that the scientists who reported the find have now admitted to making a mistake.

The team missed a key detail in its analysis of galactic dust, the rumours say, making it more likely that the signal came from a source other than gravitational waves.

Physicist Adam Falkowski of the Laboratory of Theoretical Physics of Orsay, France, on Monday reported that 'experts now put a finger on what exactly went wrong in BICEP' in a controversial post.

'Among this understandable excitement, we have been aware that the signal has to be confirmed by other experiments before the discovery is established,' he wrote.

However, the team behind the experiment has hit back.

'We've done no such thing,' principal investigator John Kovac at Harvard University told New Scientist.

'We tried to do a careful job in the paper of addressing what public information there was, and also being upfront about the uncertainties.

'We are quite comfortable with the approach we have taken.'

Scientists, from left, Clem Pryke, Jamie Bock, Chao-Lin Kuo and John Kovac smile during a news conference at the Harvard-Smithsonian Center for Astrophysics in Cambridge to announce their groundbreaking results on gravitational waves

However, confirmation of the experiment won't be known until another group either supports or opposes their finding, which could happen later this year.

According to Albert Einstein when something very explosive like this happens it leaves ripples in space-time known as 'gravitational waves'.

The very first gravitational waves can tell us about the birth of the universe and scientists have discovered they leave imprints in cosmic microwave background radiation - the afterglow of the Big Bang - as they pass through space.

The theory suggests that this intial spurt would have taken the infant universe from something infinitely small to something close to the size of a marble.

Earlier this year experts hailed the experiment as a massive step forward - but admitted the theory needed more work.

'It's just unbelievable quite honestly,' Professor Peter Ade, who helped build the instrument that detected the waves, told MailOnline.

'This is confirming what is, to me, a wacky idea.

'The next step is quite clear; to confirm the data with another technology.'

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This graphic shows the universe as it evolved from the Big Bang to now. Nasa scientists believe that the universe expanded from subatomic scales to the astronomical in just a fraction of a second after its birth

The finding by the BICEP2 telescope (pictured) in the South Pole could rank with the greatest discoveries about the universe over the last 25 years

Researchers at the Harvard-Smithsonian Centre for Astrophysics in Massachusetts built super-sensitive radiation detectors and installed them in the BICEP2 radio telescope at the South Pole to find these 'ripples in the sand.'

Nine years later they found these swirling patterns in cosmic background radiation created by the gravitational waves caused by the very beginnings of the universe.

Many scientists already believed that an initial, extremely rapid growth spurt happened, but finding this evidence has been a key goal in the study of the universe. 

The moment professor hears ripples in space time have been...

The results have been described as 'spectacular', and are expected to result in a Nobel prize for the scientists

The discovery gives us a window on the universe at the very beginning when it was far less than one-trillionth of a second old. The work still has to be reviewed by other scientists, but there is already talk of a Nobel prize.

'It's what's I would term Nobel prize winning physics,' continued Professor Ade. 'Just who that prize goes to, however, will be up for debate.'

Cosmic Microwave Background radiation, or CMB for short, is a faint glow of light that fills the universe. Pictured is the microwave radiation from the whole sky, captured by the European Space Agency's Planck satellite

According to Albert Einstein when something very explosive like this happens it leaves ripples in space-time known as 'gravitational waves'

'It's just amazing,' added theoretical physicist Lawrence Krauss of Arizona State University, who was not involved in the work. 'You can see back to the beginning of time.'

Another outside expert, physicist Alan Guth of the Massachusetts Institute of Technology, said the finding already suggests that some ideas about the rapid expansion of the universe can be ruled out.

Right after the Big Bang, the universe was a hot soup of particles. It took about 380,000 years to cool enough that the particles could form atoms, then stars and galaxies.

Billions of years later, planets formed from gas and dust that were orbiting stars. The universe has continued to spread out.

Professor Krauss said he thinks the new finding could rank with the greatest discoveries about the universe over the last 25 years, such as the Nobel prize-winning discovery that the universe's expansion is accelerating.

The new results were announced by a collaboration that includes researchers from the Harvard-Smithsonian Center for Astrophysics, the University of Minnesota, Stanford University, the California Institute of Technology and Nasa's Jet Propulsion Laboratory.

The team plans to submit its results to a scientific journal this week, said its leader, John Kovac of Harvard.

This image shows temperature fluctuations, indicated by variations in colour, of the cosmic microwave background (CMB). Researchers say since the CMB is a form of light, it exhibits all the properties of light, including polarisation (shown by black lines). The changes in polarisation are thought to be caused by gravitational waves

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The 14-billion-year-long history of our universe. It shows the main events that occurred between the initial phase of the cosmos -- where its properties were almost uniform and punctuated only by tiny fluctuations - to the cosmic structure that we see today, ranging from stars and planets to galaxies and galaxy clusters

A telescope at the south pole, called BICEP2 (Background Imaging of cosmic Extragalactic Polarisation) was used to search for evidence of gravitational waves. BICEP2 is shown here in the foreground with the South Pole Telescope in the background

For their research, astronomers scanned about two per cent of the sky for three years with a telescope at the South Pole, chosen for its very dry air, to aid in the observations.

They were looking for a specific pattern in light waves within the faint microwave glow left over from the Big Bang.

The pattern has long been considered evidence of the rapid growth spurt, known as inflation. Professor Kovac called it 'the smoking gun signature of inflation.'

The scientists said the light-wave pattern was caused by gravitational waves, which are ripples in the interweaving of space and time that sprawls through the universe.

The BICEP2 telescope's focal plane uses novel technology, developed at Nasa's Jet Propulsion Laboratory, to build an array of devices that use superconductivity to gather, filter, detect, and amplify polarised radiation from the cosmic microwave background. Each pixel is made from a printed antenna sensitive to polarised millimeter-wave radiation

A full-sky map of the oldest light in the universe. Colors indicate 'warmer' (red) and 'cooler' (blue) spots. Nasa has called this image the best baby picture of the Universe ever taken

If confirmed, the new work would be the first detection of such waves from the birth of the universe, which have been called the first tremors of the Big Bang.

Arizona State's Krauss cautioned that it's possible that the light-wave pattern is not a sign of inflation, although he stressed it's 'extremely likely' that it is.

It's 'our best hope' for a direct test of whether the rapid growth spurt happened, he added.

Professor Krauss and other experts said the results must be verified by other observations - a standard caveat in science.

Marc Kamionkowski, a theoretical physicist at Johns Hopkins University who didn't participate in the work, called the detection of the light-wave pattern 'huge news' for the study of the cosmos.

'It's not every day you wake up and learn something completely new about the early universe,' he said.